Effect of composition on the dielectric properties and thermal conductivity of α-SiAlON ceramics

In this study, a series of dense Y m /3 Si 12-( m + n ) Al m + n O n N 16- n ( m = 1.1–1.5, n = 1.0) ceramics were prepared by hot-pressing at 1900 °C for 1 h. The effects of composition on the thermal conductivity, dielectric, and wave-transparent properties of Y-α-SiAlON ceramics were investigated. The X-ray diffraction (XRD) results showed that all ceramic samples exhibited a pure α-SiAlON phase. The dielectric properties of Y-α-SiAlON at 1 kHz–120 MHz and 8.2–12.4 GHz were investigated. The results indicate that a smaller m value leads to weaker ion and interfacial polarisations, resulting in a lower dielectric constant. The three-dimensional relationship between microwave transmittance, frequency, and sample thickness was calculated by simulation, and the results showed that Y 0.40 Si 9.8 Al 2.2 O 1.0 N 15.0 had the best wave-transparent properties. The thermal conductivity of the Y-α-SiAlON ceramics showed a decreasing trend with increasing m value and temperature. The single-phase dense Y 0.50 Si 9.5 Al 2.5 O 1.0 N 15.0 exhibited the minimum thermal conductivity, which was 9.75–5.21 W/m·K (20–1000 °C). Therefore, Y-α-SiAlON ceramics are expected to be promising high-temperature window materials owing to their excellent thermal insulation and wave-transparent properties.